The present disclosure relates to a positively chargeable toner for electrostatic latent image development.
From a viewpoint of energy saving and apparatus miniaturization, a toner is desired to have excellent low-temperature fixability such as to be favorably fixable with minimal heating of a fixing roller. In order to produce a toner having excellent low-temperature fixability, it is common to use a binder resin having a low melting point or glass transition point, and a releasing agent having a low melting point. Therefore, when such a toner is stored at high temperatures, toner particles in the toner may aggregate. Aggregated toner particles tend to have a reduced electrostatic charge compared to other toner particles that are not aggregated.
In order to improve low-temperature fixability, high-temperature stability, and blocking resistance, a toner including toner particles each having a core-shell structure is used. In a toner particle having a core-shell structure, a toner core containing a low-melting-point binder resin is coated by a shell layer containing a resin having a higher glass transition point Tg than a glass transition point (Tgt) of the binder resin contained in the toner core.
As an example of a toner including toner particles having a core-shell structure such as described above, a toner has been proposed including toner particles in which toner cores having a softening temperature of no less than 40° C. and no greater than 150° C. are each coated by a thin film containing a thermosetting resin.